Apparatus and method for volumetric reduction of polymeric material

ABSTRACT

The present invention is an apparatus and method for volumetric reduction of polymeric material and in particular synthetic polymeric textile materials. Such materials are typically used in hospital operating rooms and have material memory meaning that they re-expand after compression. Consequently they are difficult to process as waste material. The present invention is a method and apparatus for thermally compacting a polymer comprising a first and second heated surface inclined downwardly towards each other and providing with a passage at their lower ends through which melted polymeric material may pass.

Disposable synthetic polymeric textile materials are used particularlyin hospital operating rooms as a sterile cover to protect patients andinstruments from contamination and cross infection. Generically thematerial is known as sterile wrap or “Blue Wrap” and is available inmany proprietary brands such as “Kimguard™” manufactured by the KimberlyClark Corporation, and “DuraBlue™” manufactured by Cardinal Health.Other synthetic materials are known and used in hospitals such as Tyvek™manufactured by Dupont.

The material is generally manufactured from non-woven synthetic polymerssuch as polypropylene or polyethylene and has the advantage of beingtough and difficult to tear, non-absorbent, easy to manufacture indifferent sizes and is supplied as a sterile product. The material canalso be manufactured to allow a predetermined air flow through thematerial when it is desirable to do so. Typically the material ismanufactured from 100% polypropylene with a SMS(spunbond-meltblown-spunbond) structure. The material can bemanufactured to allow a predetermined airflow through the material whenit is desirable to do so. Other disposable products that aremanufactured from these and similar materials include irrigation bags,hypodermic syringes, specimen and instrument trays, disposable forcepsand sharps devices and medicine delivery systems, all can be processedby the current invention.

The disposable material offers many financial advantages overtraditional textiles which necessitate high energy costs to launder themtogether with the use of potable water and chemicals such as detergentswhich can pollute downstream water courses. After use the material iscategorised as either inert waste or bio hazardous waste and is usuallydisposed of by either incineration or landfill. It is estimated thatglobally 7000 tonnes of such material is destroyed daily after a singleuse. This material is potentially a valuable resource for recycling butissues in respect of sanitation and high volume to weight ratios maketransportation expensive.

It is known that mechanical compaction machines or balers have been usedto try and reduce the volume of the material for transportation butthese are not efficient as the material exhibits “memory” and re-expandafter compression, are slow and labour intensive to operate and thematerial still requires handling as bio hazardous material.

Reference is made to EP0556282 by the present inventor. These machines(inventions) were developed to volumetrically reduce foamed plasticproducts such as expanded polystyrene or styrofoam fish boxes. Themachines comprise of electrically heated vessels and the material ismelted and converted to a liquid which flows into a receptacle below theheated plates.

As the “blue wrap” synthetic textile material exhibits totally differentmelting characteristics to expanded polystyrene then such an apparatusis not suitable for volumetric reduction and sterilisation. This isbecause the density of the expanded polystyrene is significantly lessthan the synthetic textile material as it is cellular with large voidsbetween the thin cell walls. As a consequence, on application ofrelatively low heat, the thin cell walls of the expanded polystyrenerupture and lose their physical integrity and will flow down arelatively shallow draft angle of the heated plates within an inclinerange of 45 to 60 degrees to a vertical axis which is advantageous as itallows a larger surface area inside a small machine to deal with aproduct that has a very unfavourable and high volume to weight ratio.

The synthetic textile material would not melt in a similar manner forseveral reasons. This is a result of molecular orientation and themanner in which polymer chains position themselves in the meltingcavity. Polymers near the wall of the heated plates orient themselves bystraightening out, while polymers near the centre of the load placed inthe machine tend to stay coiled and do not melt. As a consequenceconfirmation when testing resulted in the un-melted material remainingstatic and inhibiting the melted material from flowing as wasanticipated.

The primary reason is considered to be the textile material, compared toexpanded polystyrene is denser and has thicker cell walls as aconsequence a different polymer chain. From experiment it was found thatthe thicker cellular walls of the material acted as an insulator andwould not allow heat to be conducted easily into the subsequent multiplelayers of material that were placed in the machine for melting. As thematerial is a textile with a large surface area, increases intemperature also did not assist as they created a thermal uplift whichmoved the heated material away from the conducted heat source so apartial melt only was achieved which did not flow. It was also apparentthat the temperature at which the material plasticises was considerablyhigher than expanded polystyrene.

The objective of volumetric reduction and sterilisation of the materialis to allow the material to be transported without expensive specialistwaste handling techniques to a recycling facility. At best the materialwill be recycled into other useful products and at worst it will besignificantly volumetrically reduced or densified to considerably reducethe energy cost and environmental impact of transporting the materialfor any other method of disposal.

The present invention provides a method and apparatus to bothvolumetrically reduce polymeric textile material and also polypropyleneat the point of its use and to sterilise it.

According to the present invention there is a thermal compactingapparatus for thermally compacting a polymer comprising a first andsecond heated surface inclined downwardly towards each other andprovided with a passage at their lower ends through which melted polymermay drain.

The apparatus is beneficially a polymeric textile and/or polypropylenethermal compacting apparatus, and even more beneficially a syntheticnon-woven polymeric textile and/or polypropylene thermal compactingapparatus. “Blue wrap” is such a material.

Such an apparatus is beneficial as waste synthetic polymeric textilematerial and polypropylene can be thermally compacted at source and willinclude materials, for example, to include sterilised sheets in varioussizes, clothing and uniforms, bedside and window curtains, cleaningcloths, instrument pouches and any other product manufactured ofsynthetic polymeric textile material, and other products such aspolypropylene saline bags. This provides a significant benefit ofproviding a volumetrically reduced and sterilised product that can berecycled and also significantly reduces transportation costs associatedwith a high volume product. The apparatus is also suitable for thermallycompacting and sterilising other polypropylene products such as salinebags.

The first heated surface is beneficially inclined at less than 45degrees to a vertical axis, and preferably the second heated surface isinclined at less than 45 degrees to a vertical axis. It has beendetermined that such a range of incline is beneficial as it wasunexpectedly found that although the synthetic polymer textile materialwas able to melt and collapse by using a prior art arrangement such asdescribed in EP0556282, it did not flow because the material simplycollapsed and remained on the heated surfaces and eventually carbonised.Increasing the incline of the first and preferably second heated surfaceresulted in improved flow of the melted product.

The first heated surface is beneficially inclined to a vertical axis ofbetween 25 degrees and less than 45 degrees, and preferably wherein thesecond heated surface is inclined to the vertical axis between 25degrees and less than 45 degrees.

The first heated surface may be inclined at an angle of between 25 and45 degrees to a vertical axis and preferably wherein the second heatedsurface is inclined at an angle of between 25 and 45 degrees to avertical axis.

The first and preferably the second heated surfaces are beneficiallyarranged to be heated to a temperature in the range 250° C. to 310° C.,and more preferably between 275° C. and 295° C. and even more preferablyat substantially 285° C. The first and preferably second heated surfacesinclude at least one heating element. Utilising the claimed temperatureranges also ensures sterilisation of the material. The arrangement ofEP0556282 is incapable of operating at such temperatures. During theprocess of converting the material from a solid to a liquid thetemperatures utilised have been found to destroy biological pathogens.This is assisted by the fact that during the process the material flowsinto a receiver as defined below that keeps the material at a raisedtemperature such as 260° C. for 30 minutes. This is important because“dry heat” is not always successful in sterilisation and the presentlyclaimed apparatus and process can be considered to provide “conductivewet” heat.

Unlike conventional plastic injection moulding, vacuum forming orextrusion processes which are commonly used to melt and mouldpolypropylene materials, the process temperature of the invention isdifferent and has been determined to fall within the claimed temperaturerange. This is because the other conventional methods of melting andforming the material utilise not only heat but pressure such as amechanical screw or a vacuum to assist in processing. Unlike thisequipment the invention does not require pressure but relies on gravityto feed the machine so the melting temperature is crucial as too low atemperature inhibits the process and too high a temperature can damagethe melt index of the material making it unsuitable for recycling or insevere instances it could create a combustion risk. The temperaturerange is beneficially controlled by maintaining power to the heaterplates on demand via contactors or solid state relays which switch onpower as a result of a programmable logic controller or temperaturecontroller sensing the set operating temperature via, for example,thermocouple sensors which are positioned inside the body of thematerial that provides the heated surface(s). The heated surfaces areeach beneficially provided by aluminium plate heaters having at leastone heating element therein. The heating element may be an electricresistance heater for example. An improved plate heater is achievedthrough provision of a sprayed (preferably plasma) heating element whichin itself is in plate form. A preferable structure is a substrate whichcan be made of stainless steel, fibreglass or silicon for example. Aplasma sprayed heater layer is provided thereon, preferably separatedfrom the substrate by an insulator material, and a final insulationlayer is provided onto the heating layer. This achieves a very thinheater plate and thus achieves fast heating and cooling.

The temperature profile of the first and preferably the second heatedsurfaces may increase towards the passage. The at least one heatingelement in the first and preferably the second heated surfaces isbeneficially configured such that the temperature profile of the firstand preferably second heated surfaces increases towards their lower endsand the passage. This further improves in melting and transfer of thematerial towards the passage. The temperature range of the first andbeneficially second heated surface changes between substantially 260° C.at a leading edge to substantially 295° C. at an edge adjacent thechannel. This assists in achieving a tumbling effect on the material.This creates a physical phenomena whereby the faster melting materialplasticises and ‘slips’ or moves downwards in a fluid manner to exit theheating zone and creates a void which encourages the material above itto fill. This is contrary to common practise in waste materialprocessing where heating plates are designed to ensure predictable andeven heat transfer.

The first and second heated surfaces beneficially define a heating zonetherebetween.

A further problem is that on leaving the heated zone and flowing throughthe passage the material has a propensity to solidify and as aconsequence create solidified pillars of material between the heatedsurfaces and the receiver which creates a blockage and stops the removalof the receiver from the machine. Furthermore, at the end of a meltingcycle when the heated surfaces are cooling and the heating elementsisolated from power, residual amounts of material are left on the heatedsurfaces as the heated surfaces, which may be aluminium plates orprinted circuit board plates, cool quickly.

A lower end(s) of the first and preferably second heated surfacesbeneficially includes an insulating material for reducing the rate ofcooling of the first and preferably second heated surfaces. Theinsulating material is beneficially provided applied to the heated plateand is beneficially provided on the heated plate out of or away from theflowpath of the material. This encourages material to vacate the platesand to exploit residual latent heat. A layer of micro-porous insulationis beneficially utilised. It is preferably applied to the rear of thetwo main plate heaters to assist the final moments of the process.

The passage beneficially comprises a longitudinal length and a width,where the width is preferably in the range 15 mm to 75 mm. Thelongitudinal length is parallel to the leading edge of the first andsecond plates. It is important that the separation between leading edgesof the plates, analogous to the width of the passage, is carefullyselected. A range of 15 mm to 75 mm is a workable range, however, areduced separation is preferred for pure forms of waste material whereasa passage width of 75 mm can accept a significant variety of mixedwaste. For example, as well as polymeric textile material and/orpolypropylene other materials in the waste may be present such asVelcro, nylon cuffs, metal poppers etc which may not melt. However, itis beneficial that these materials are encapsulated in the melted andsubsequently solidified waste material. For this reason a greater widthof the passage is beneficial to ensure that this material may passtherethrough. As such it has been found that substantially 70 mm ofseparation between the plates is optimal for mixed waste material.

A receiver is beneficially disposed in a receiving zone for receipt ofmelted synthetic textile material from the passage. A heating element isbeneficially provided configured to supply heat to the receiver. Thereceiver is beneficially heated in order that the material flows onto aheated surface and does not immediately solidify. This ensures flow ofthe material, and also provides a dwell time for the material to ensuresterilisation. The dwell time may for example be between 15-60 minuteswith a preferred dwell time being substantially 30 minutes. Thetemperature may be at approximately 260° C. The heating elementbeneficially comprises a heating plate. The receiver is beneficiallyremovably mounted with respect to the heating plate.

A cooling arrangement is beneficially provided for cooling the receiver.The heating element and cooling arrangement beneficially provide achangeable heating and cooling surface for heating or cooling thereceiver as appropriate. The heating and cooling element may thereforepreferably be integrated to provide an optional heating or coolingsurface for heating or cooling the receiver. The receiver beneficiallytakes the form of a tray. Even more beneficially, the receiver is in theform of a mould receptacle.

The apparatus beneficially comprises a housing for accommodating thefirst and second heated surfaces wherein the housing is in fluidcommunication with a filter arrangement for filtering gases receivedfrom the housing, the apparatus further comprising a condenserarrangement positioned intermediate the housing and the filterarrangement. The filter arrangement is arranged to receive output gasesfrom the housing. Such gases may be harmful and it is important thatthese are filtered prior to release to the atmosphere. It is beneficialto provide a condenser arrangement positioned intermediate the housingand the filter arrangement in fluid communication with both the housingand filter arrangements. The condenser arrangement provides asignificant benefit in that it reduces the temperature of the exhaustgases from the housing and condenses any fluid which is in the exhaustgases. This improves the effectiveness of the filter arrangement andminimises the impact of the apparatus with respect to release of odours.

The cooling arrangement beneficially includes a heat exchange unit(commonly termed a chiller unit in this field) and heat transferarrangement in fluid communication, wherein heat from the receiverand/or the heating element if transferred to the heat transferarrangement. An expansion tank is beneficially positioned intermediatethe heat exchange unit and the heat transfer arrangement and in fluidcommunication with both the heat transfer arrangement and the heatexchange unit. As the melted waste material has to be reduced intemperature to make it safe to handle this is achieved utilising acooling arrangement made up of a heat exchange unit and heat transferarrangement. To improve the efficiency of the heat exchange unit and toprevent damage, an expansion tank is beneficial intermediate the heatexchange unit and heat transfer arrangement to act as an additional heatsink to assist in reducing the process temperature.

After a predetermined period of time and temperature the heatingelements in the machine are isolated and cool down to allow thesolidification of the material and its removal from the machine. Incertain applications such as large teaching hospitals with severaloperating rooms, the throughput of the machine would be insufficient tocope with demand as a result of the time it takes to cool the liquefiedmaterial. Accordingly, a heated plate may be provided under the receiverwhich would also contain cooling circuits which would be operated at theend of the heating cycle to accelerate the cooling time of the machine.

A cooling zone may be provided remote from the receiving zone andheating element (if provided) and a transfer arrangement is beneficiallyprovided for transferring the receiver to the cooling zone. A pluralityof individual locations within the cooling zone is beneficially providedeach configured to receive a receiver. This means there can be coolingof more than one filled receiver simultaneously. This means that aircooling can be utilised. Such a transfer arrangement enables cooling ofthe waste material in a receiver without the essential requirement for acooling arrangement. This is beneficial for certain applications as thecost of the equipment may be reduced due to the removal of therequirement for a cooling arrangement. An additional benefit is thathigh volumes of material can be processed as cooling of a receiver canbe achieved at the same time as processing of further waste materialinto a further receiver. The transfer arrangement may be of a differentform and may comprise, for example, movement of the receiver on a rollerbearing track, high temperature conveyor or a carousel arrangement.

The first and preferably the second heated surfaces are preferablydefined by first and preferably second heating plates respectively. Thefirst and preferably second heating plates may be formed of aluminiumwhich is preferably cast. The plates beneficially incorporate at leastone heating element therein. The heating elements are beneficiallyelectrically heated.

It is beneficial that the first and preferably second heated surfacesare provided by printed circuit board plates. Such plates are beneficialas they are significantly reduced in thickness compared to traditionalaluminium heating plates meaning that the plates may be heated up to thedesired temperature significantly quicker than with an aluminium castplate.

The first and preferably the second heated surfaces are beneficiallyformed with a coating thereon to assist transfer of material thereover.A suitable coating is, for example, Teflon®.

A monitoring and recording arrangement is beneficially provided formonitoring and recording first and preferably second heated surfacetemperatures and preferably dwell time of melted material transferredthrough the passage to the receiver. This is beneficial to ensure thatthe material is sterile and has been processed at a sufficiently hightemperature and dwell time to ensure complete sterility of the processedmaterial.

An exhaust arrangement is beneficially provided for removing gases fromthe process.

A door lock is beneficially provided configured such that the doorcannot be opened to the apparatus until the temperature within theapparatus has dropped to a safe level. Accordingly, the apparatuscomprises a door which is beneficially electrically operated. A sensorwithin the apparatus is arranged to measure the temperature within theapparatus. It is beneficially provided with a control arrangement whichcontrols the door lock. The controller arrangement beneficially includesa monitoring and recording arrangement.

Also according to the present invention there is a method of thermallycompacting polymeric textile materials and/or polypropylene comprisingthe steps of introducing polymeric textile material and/or polypropyleneinto a heating zone defined between first and second heated surfacesinclined downwardly towards each other and being provided at their lowerends with a passage through which polymeric textile material and/orpolypropylene may drain.

The present invention will now be described by way of example only withreference to the accompanying drawings in which:

FIG. 1 is a schematic front view of an apparatus according to anexemplary embodiment of the present invention.

FIG. 2 is a more detailed schematic representation of an apparatusaccording to an exemplary embodiment of the present invention showing anoptional cooling arrangement and showing an exemplary control panel.

FIG. 3 is a schematic perspective view of an exemplary embodiment of thepresent invention with the housing removed.

FIG. 4 is a schematic perspective view of an exemplary embodiment of thepresent invention as shown in FIG. 3 in an alternative operationalconfiguration.

FIG. 5 is a schematic perspective view of an exemplary embodiment of thepresent invention showing in addition a cross sectional view through anexample of a component of the condenser arrangement.

FIG. 6 a is a schematic cross-sectional plan view of a heated plateaccording to an exemplary embodiment of the present invention. FIG. 6 bis a schematic cross-sectional view of an end of the heated plate.

FIG. 7 is a schematic cross-sectional plan view of a heating and coolingplate for the receiver for use in an exemplary embodiment of the presentinvention.

Referring to FIG. 1 there is an exemplary embodiment of the presentinvention. The apparatus is shown without a door which is closed duringuse and hides the internal components provided within the housing (2)and provides a seal for when the apparatus is in use. The apparatusincludes first and second heated plates (4,6) which are beneficiallyformed from cast aluminium and are electrically heated being providedwithin the housing (2). The housing (2) defines an opening (8) in itsfront. The first and second plates (4,6) are inclined downwardlyconfigured to funnel waste material such as synthetic polymeric textilematerial downwardly toward a channel (10) provided between the lowerends of the plates (4,6). The waste material is therefore input into thehousing (8) through the front opening, however, it is envisaged that oneor more openings may be provided in another portion of the housing (2)such as in the top or in the side of the housing but beneficially abovethe first and second plates (4,6).

In the examples shown the first and second plates have identical anglesrelative to the vertical axis. It will be appreciated, however, that theangle of the first and second plates may be different to each other. Theincline angle of the heated surfaces to the vertical is beneficiallyless than 45 degrees, and is beneficially in the range 25 degrees toless than 45 degrees. This is to ensure that the material melts andcollapses and subsequently flows through the channel (10).

The first and second plates (4,6) are beneficially coated with Teflon®,and may be ceramic or hard anodised. A receiver (12) is providedsupported below the channel (10) arranged to collect melted materialtherefrom. The receiver (12) removably seats into a docking zone (14)which is provided to ensure alignment of the receiver (12) with thechannel (10). The receiver (12) seats onto a plate (16). The plate isbeneficially arranged to be heated and includes one or more heatingelements therein, preferably of the type of electrically resistiveheating elements. The plate (16) may also include one or more coolingcircuits comprising a channel to transfer coolant therethrough forincreasing speed of material processing. The plate (16) also includes athermocouple to monitor the temperature of the plate (16). Thermocouples(18) are also provided on the heated plates (4,6) to monitortemperature. Temperature information from the thermocouples (18) istransferred to a control arrangement (20). The control arrangement (20)includes a control panel and serves to control the electrical supply tothe heating elements within the heated plates (4,6) and the plate (16).The control arrangement controls the time of heating of the heatedplates (4,6) and the plate (16) and also controls actuation of thecooling circuit in the plate (16). The control arrangement also providescontrol to an extraction arrangement (22) which includes a filtrationcabinet for transfer of gases from the apparatus through an inlet (24),through a filtration cabinet (26) and out of an exhaust (28). Materialleaving the heated zone defined between the heated plates (4,6) andflowing into the receiver (12) has a propensity to solidify and as aconsequence creates solidified pillars of material between the heatedplates (4,6) and the receiver (12) which can create a blockage and stopthe removal of the receiver from the apparatus. Furthermore, at the endof a melting cycle when the electrical plates are isolated from power,residual amounts of material may be left on the plate heaters as thealuminium cools quickly. To encourage material to vacate the plates andto exploit residual latent heat it has been determined that a layer ofmicro-porous insulation should be applied to the rear of the two mainplate heaters to assist the final moments of the process. It has alsobeen determined that to assist in the material sliding down the platesit is preferable to coat them with a polytetrafluoroethylene (PTFE) orTeflon® coating. This assists the process by sealing the porous surfaceof the aluminium electrical heat plate heaters which enhanced thematerial's passage or slip factor as it did not permeate into thesurface of the plate heaters when fluid. The PTFE's melting temperatureis typically 326° C. but the operating temperature of the Teflon® duringthe heating process is less than 200° C. making it suitable for purposein respect of health and safety issues.

It is further improved by the provision of the heated plate (16). It ispreferred that the temperature of the heated plate (16) is set to beapproximately 20° C. lower than the set point of the heated plates(4,6). From trial it has been determined that the optimum temperature ofthe plate (16) is 265° C.

After a predetermined period of time and temperature the heatingelements in the machine are isolated and cool down to allow thesolidification of the material and its removal from the machine. This isfollowing a material dwell time within the receiver where heat issupplied ensuring sterilisation of the material.

It has been determined that in certain applications such as largeteaching hospitals with several operating rooms, the throughput of themachine would be insufficient to cope with demand as a result of thetime it takes to cool the liquefied material. In this situation it isintended that in one embodiment the heated plate under the removablereceiver (12) would also contain cooling circuits which would beoperated at the end of the heating cycle to accelerate the cooling timeof the machine.

The receiver (12) may rest or be otherwise disposed on the heated plate(16) wherein the heated plate (16) may be cast aluminium. In the eventthat the heated plate also comprises cooling elements, circuitry fluidis passed through the cooling pipes which may have been chilled with anindustrial chiller to sub-zero temperatures. This fluid has an inhibitoradded such as glycol to stop it from freezing. At the end of the heatingcycle the fluid can be diverted, for example, from the heat exchangeunit (40) as represented in FIG. 2 via a two-way solenoid valve (43)where the fluid is violently converted to steam. The calorificconversion from fluid to steam acts to initiate an immediate and rapiddrop in temperature. The cooling fluid can be supplied with or withoutthe addition of chemicals to inhibit the freezing temperature of thefluid and can be delivered in addition to the heat exchanger (chillermachine) by simply attaching to a mains water supply with our withoutpumps and a water tank as either an open or closed circuit. It will befurther appreciated that the cooling arrangement may comprise a heattransfer arrangement which is alternative to the cooling circuitprovided within the heating plates. Such a heat transfer arrangement orcooling circuit may be provided separate to the heated plate (16) asrepresented by reference number (44) in FIG. 2. A heat transferarrangement (44) independent of the heated plate (16) or a heat transferarrangement comprising cooling circuits within the heated plate (16) areenvisaged. It is further envisaged that intermediate the flowpathbetween the heat exchange unit (40) and the heat transfer arrangement(44) is an expansion tank (46). At the end of the heating cycle themelted waste material has to be reduced in temperature to make it safeto handle. As described this is typically via a heat transferarrangement comprising a cooling circuit provided within the heatedplate (16). At the end of the heating cycle the two-way solenoid valve(42) shares flow of cooling fluid from a condenser arrangement (48)which is positioned intermediate the flowpath between the housing (2)and the filter arrangement (26). As the heated plate (16) is operatingin excess of 200° C., the initial flow of fluid converts to superheatedsteam and this calorific conversion is fundamental to the coolingprocess as this accelerates the cooling of the heated plate (16). Atthis temperature and pressure the return flow would ordinarily damage aconventional heat exchange unit accommodated in a chiller machine so anexpansion buffer tank (46) is connected in fluid communication betweenthe heated plates (16) and the heat exchange unit (40) to avoid damageand to act as an additional heat sink as the surplus fluid in theexpansion buffer tank (46) assists greatly in reducing the processtemperature.

It has also been determined that the assisted cooling of the materialafter melting offers a considerable reduction in odour. The meltedmaterial does not liberate VOC's as the process can be considered asimple reversal of the original manufacturing process but as the polymerunder temperature is an aromatic it is desirable to remove odours whichcould be unfamiliar in the workplace operating the machine. As themelting polymer is an aromatic an embodiment of the invention willutilise a variable speed exhaust fan (50) which will accelerate at theend of the process when the access door (not shown) is opened to reducethe emissions of odour. This fan (50) also assists in cooling themachine at the end of the heating process and to maintain a partialvacuum in the machine to reduce the opportunity for odour to escape fromthe machine. The exhaust (28) from the machine is filtered through afilter arrangement (26) preferably comprising both a HEPA and activatedcarbon filter to reduce emissions in respect of fumes and odour.

During operation of the apparatus a partial vacuum is maintained in thehousing (2) (cabinet/hopper) while maintaining a flow of air from thehousing using the electric fan (50) which flow is conveyed into thefilter arrangement (26). The fan is beneficially a variable speed fanand works at low speed when the waste material is being heated and athigh speed during the cooling cycle or when the door of the housing (2)is open. The purpose of the partial vacuum is to eliminate emissions ofunfamiliar odours into the workplace from the housing (2) and thepurpose of the filter arrangement (26) is to reduce the odour of theexhaust gases to the atmosphere.

The exhaust fumes are hot and can contain plasticising oils that areliberated from the polymer during the process. The fumes are passedthrough the filter arrangement such as a paper or textile bag filter andthen through an activated chemical filter such as a carbon filter tominimise odours from the machine. Filters can lose their efficiency ifhot fumes are passed through them and their longevity is reduced if theybecome blocked with plasticising oil. To reduce the temperature of theexhaust gases before they reach the filter arrangement (26) and tocapture any plasticising oils, the gases are passed through a condenserarrangement (48). This may comprise a condenser plate which may consistof a hollow aluminium finned vessel. The condenser plate may, however,be made of any conductive alloy. The vessel is finned to increase thesurface area in contact with the airflow. During the operation of theapparatus, a chilled fluid is passed through this vessel which assistsin reducing the temperature of the exhaust gases and also assists incondensing any fluid which is in the exhaust gases. The fins of thecondenser are represented in FIG. 5 and are beneficially verticallyaligned allowing the collected fluid to flow easily downwards to a pointat which they can be collected for disposal or recycling. It is alsopossible to utilise, in an alternative configuration, a spiral helicalfinned tube to achieve the same effect. The exhaust pipe (52) as bestshown in FIG. 5 is elongated to increase the dwell time of the exhaustgases.

To ensure the safety of operators an electrical door lock may beutilised which will not allow the door to be opened during the processuntil the temperature of the inside of the machine has dropped to a safelevel. This electrical door lock will be interlocked with thetemperature control software running in the control arrangement (20) andthe machine and will only open when thermocouple sensors confirm theambient temperature inside the machine.

It is anticipated that the machine will be fitted with a telemetrydevices to allow the machine operators from a distance to interrogateand log the machine cycle times and record any deviation from normaloperation which may necessitate investigation or repair.

The apparatus may be manufactured from stainless steel material as it isintended to be used out of doors but alternatively could be manufacturedfrom ordinary steel with a protective coating or even an insulatedpolymer such as GRP.

As the apparatus ensures sterility of the material after melting anembodiment of the invention contains a data logger to record both timeand temperature to confirm that the material has been processed at asufficiently high temperature and dwell time to ensure completesterility of the processed material.

Referring now to FIG. 3, there is a schematic perspective view of anembodiment of the present invention that utilises a different coolingmechanism to the arrangement as presented in FIG. 2.

The apparatus as previously described utilises fluid and air cooling tomake the processed material safe to handle by solidifying the liquidpolymer after the heating process. Whilst the process works and issatisfactory it is expensive as it requires a chiller machine, castcooler unit, expansion tank and special solenoid valves and hightemperature high pressure cooling.

In applications where high volumes of material are to be processed thecost/value benefit of the machine using this equipment works but inapplications where there are lower volumes of materials the cost of thisequipment may be prohibitive in the cost benefit relationship.

In such applications it is proposed to air cool the material and this isachieved by locating the receiver (12) on a transfer arrangement such asa roller bearing track, a high temperature conveyor or a carouselarrangement.

In this embodiment no cooler arrangement is used and typically theheating element is raised or lowered by a lever (54) to make contactwith the receiver (12). At the start position the heating element (16)touches the receiver (12) during heating. At the end of the process theheating element (16) is dropped from the contact position by the leverand the full receiver (12) is moved sideways on the roller track to thecooling position and then cooled. An empty receiver (12) is then putinto position and filled and at the end of the next cycle the receiver(12) is moved to the alternative cooled position. At the end of thethird cycle the first cooled receiver (12) is either removed from theapparatus and stored in a rack or put into a storage position at thebottom of the apparatus until each position is full and the first blockis then removed. In this instance the material has the benefit ofseveral hours of cooling without the need for forced fluid cooling by amachine.

As such as presented in FIG. 3, receiver (12 a) is in the coolingconfiguration and receiver (12 b) is in the receiving configuration.Further shown is rail (56) along which the receivers can slide alongsliders (58). The handle is presented in the raised or ‘on’configuration which means that the receiver receiving the waste materialis prevented from moving. Rear carriage supports (60) are identified.FIG. 4 presents the same embodiment as presented in FIG. 3, however, thefill receiver (12 b) has moved to a cooling position and a new emptyreceiver (12 c) has been moved across to receive waste material. Theheating element (16) can be seen and the handle (54) is shown in thelowered or ‘off’ configuration allowing the receiver carriage (62) tomove.

In one embodiment forced air cooling can be achieved utilising vortexblowers. In this device compressed air is blown through a vortex blowerwhich cools the air to a very low temperature (sub-zero) and as aconsequence the material cooling is accelerated but without the need fora chiller machine.

Referring to FIG. 6 there is a schematic plan cross-sectional viewthrough an exemplary embodiment of a heated plate (4,6). The heatedplate (4,6) comprises a first or upper end (30) and a lower or secondend (32), where the second or lower end form one edge of the channel andthe other of the first or second heated plate 4,6 forms the other edgeof the channel. The lower edge (32) is beneficially chamfered as shownin FIG. 6 b. It will be appreciated from FIG. 6 a that the heatingeffect of the heating element (34) is greater towards the lower edge(32) as a result of increased volume of heating element toward the loweredge (32). This is provided to ensure continuous process of melt andflow of the waste material.

It was discovered from trial that although the largest manufacturer ofthe sterilisation wrap's melting point was cited at 150° C., the heatingsource acted as a heat sink and consequently at this temperature thematerial did not flow. To achieve a temperature conducive to achieving acontinual process of melting and flowing and to account for thermal lagthe heat source which is preferably electrical resistance heaters haveto operate to provide a heated surface temperature of between 275° C.and 295° C. The optimum set point of these heated surfaces (plates) wasdetermined to be 285° C. At this temperature the material will meltcontinually and the flow temperature rate is confined between 155° C.and 160° C. with the optimum temperature to achieve good flow ratesbeing 156° C. At this temperature the melt index of the material is notdegraded making the material suitable for recycling into new product orproducts.

Consequently the temperature range found to be suitable for the processis between 155° C. and 160° C. and this is controlled by maintainingpower to the heated plates on demand via contactors or solid staterelays which switch on power as a result of a programmable logiccontroller or temperature controller sensing the set operatingtemperature via thermocouple sensors which ideally are positioned insidethe aluminium plate heaters near the area in which the process takesplace.

The first and second plates consist of two cast aluminium electricallyheated plate heaters which are Teflon® coated as described above toassist the passage of the material after melting and one mica insulatedor cast aluminium plate heater (16) placed under the mould receptacle.It is anticipated that these heaters could also be simplified by weldingor mechanically attaching round or square tubular mineral insulatedelectrical resistance elements to substantial aluminium, non-ferrous orferrous plates which would reduce weight of the machine and the cost ofcasting and machining plate heaters. Non-ferrous materials arepreferable to ferrous materials in the construction of the heatingplates as they exhibit better thermal conductivity characteristics.

In an alternative embodiment it is beneficial to use a plasma sprayedheated plate to melt the waste material. The significant benefit of suchheated plates is their lower mass which will allow much faster heatingand cooling process times. Such heaters may be termed ‘thermal sprayheaters’, and are constructed of layered structure comprising asubstrate, and insulating layer, a heating plate plasma sprayed onto theinsulating layer and a further insulating layer forming the outerheating surface of the heater plate.

The plate (16) is identified in FIG. 7 and is a schematic cross-sectionthrough a plan view of a traditional plate (16). An electrically heatingelement (40) is provided having electric terminals (42). Furthermore, acooling circuit (44) is provided having an inlet (46) and outlet (48) tobe used to increase productivity of the apparatus.

The walls of the housing are hollow and filled with body solubleinsulation for the purpose of energy efficiency, process control andsafety. The insulation can be made from fibreglass, ceramic, silica orother insulation.

To avoid heat transfer from the chassis of the machine cooling trays canbe insulated with Aerogel material which is made from micro porousglass, silica or zeolite which protects the cooling tray from bothradiant and conducted heat.

During research a problem was encountered with heat loss and excesstemperature loss at the corners of the door of the machine which wassealed around the door with a high temperature seal that followed the 90degree angle of the door shape. As a result of experimentation the doorseal was changed to a shallow curve which created an air gap and stoppedthe heat losses.

There are a number of additional beneficial features of the presentinvention. The machine can be loaded continuously with a chute. Themachine uses an increased airflow and a moving mould plate to ejectblocks on a continuous basis. When the loading chute is opened theexhaust fan accelerates to stop fumes exiting the machine. In order toprevent degradation of the heated surfaces, an additional coating oranodizing is beneficial. This protects the heated surface and anycoating thereon such as Teflon®.

The machine can be configured such that at the end of the day'soperation or periodically can be switched into “clean” mode at whichtime the temperature in the machine increases to 400° C. to sterilizethe internal surfaces of the machine.

The machine that has variable adjustments to allow it to melt all commonpolymers in addition to “Blue Wrap”. The machine can be set to operatebetween 0-450° C. An atomiser nozzle may be positioned in the roof thatcan spray the inside of the machine with disinfecting fluids orchemicals as and when required either manually or automatically as partof a cleaning regime.

The machine is usually manufactured from stainless steel but can bemanufactured from other metals or polymeric materials such as reinforcedfibreglass and this may be painted yellow or white which is a colourknown to repel flies.

Telemetry provides for cycle times and servicing can be interrogated ata distance and adjustments made to the machine. The machine can bescaled, so for example can be reduced in size for the melting ofspecific products for example masks or hats. The machine is fullyinsulated machine that can be used in any climate. The machine may alsobe fitted with a voice card which thanks the operator for loading themachine when the door or chute is opened and can advise on machinestatus or issue operating instructions.

The machine that is painted a particular colour to deter insects, andcan be operated by induction heating not resistant heating and can beoperated by heating with superheated fluids. The machine can be operatedby heating with microwave emission.

Alpha numeric embossing may be provided in each receiver so each batchof material can be identified to a particular machine or location. Atime and temperature data logger may be provided so each batch ofmaterial can be audited and an integrated alarm and notificationproduced if a batch does not achieve the pre-set process requirements.

In one exemplary embodiment the machine cleans emissions with a plasmaburner to eliminate the requirement for a filtration system. A built infire suppressant system may be provided to legislate for maliciousdamage or catastrophic failure of the control system. This issupplemented by a thermal fuse.

The present invention has been described by way of example only and itwill be appreciated by the skilled addressee that modifications andvariations may be made without departing from the scope of protectionafforded by the appended claims.

1. A thermal compacting apparatus for thermally compacting polymericproducts comprising a first and second heated surface inclineddownwardly towards each other and provided with a passage at their lowerends through which melted polymer may drain.
 2. An apparatus accordingto claim 1, further comprising a receiver disposed in a receiving zonefor receipt of melted polymer material from the passage.
 3. An apparatusaccording to claim 2 comprising a heating element for supplying heat tothe receiver.
 4. An apparatus according to claim 2 further comprising acooling arrangement for cooling the receiver.
 5. An apparatus accordingto claims 3 and 4, wherein the heating element and cooling arrangementare integrated to provide an optional heating or cooling surface forheating or cooling the receiver.
 6. An apparatus according to claim 4,wherein the cooling arrangement includes a heat exchange unit and heattransfer arrangement in fluid communication, wherein heat from thereceiver and/or the heating element is transferred to the heat transferarrangement.
 7. An apparatus according to claim 6, wherein an expansiontank is positioned intermediate the heat exchange unit and heat transferarrangement and in fluid communication with both the heat transferarrangement and the heat exchange unit.
 8. An apparatus according toclaim 1, wherein the passage comprises a longitudinal length and awidth, where the width is in the range 15 mm to 75 mm.
 9. An apparatusaccording to claim 3, comprising a cooling zone remote from the heatingzone and a transfer arrangement for transferring the receiver to thecooling zone.
 10. An apparatus according to any claim 1, wherein thefirst heated surface is inclined at less than 45 degrees to a verticalaxis, and preferably wherein the second heated surface is inclined atless than 45 degrees to a vertical axis.
 11. An apparatus according toclaim 10, wherein the first heated surface is inclined to a verticalaxis of between 25 degrees and less than 45 degrees, and preferablywherein the second heated surface is inclined to the vertical axisbetween 25 degrees and less than 45 degrees.
 12. An apparatus accordingto claim 1, wherein the first heated surface is inclined at an angle ofbetween 25 and 45 degrees to a vertical axis and preferably wherein thesecond heated surface is inclined at an angle of between 25 and 45degrees to a vertical axis.
 13. An apparatus according to claim 1,wherein the first and preferably the second heated surfaces are arrangedto be heated to a temperature in the range 250° C. to 210° C., and morepreferably between 275° C. and 295° C. and even more preferably atsubstantially 285° C.
 14. An apparatus according to claim 1, wherein thefirst and preferably the second heated surfaces include at least oneheating element.
 15. Apparatus according to claim 1, wherein thetemperature profile of the first and/or the second heated surfacesincreases towards the passage.
 16. An apparatus according to claim 1,wherein the first and preferably the second heated surfaces are providedby printed circuit board plate heaters.
 17. Apparatus according to claim1, wherein the lower end(s) of the first and preferably second heatedsurfaces include an insulating material for reducing the rate of coolingof the first and preferably second heated surfaces.
 18. Apparatusaccording to claim 1, wherein the first and preferably the second heatedsurfaces are formed with a coating thereon to assist transfer ofmaterial thereover.
 19. An apparatus according claim 1, including amonitoring and recording arrangement for monitoring and recording firstand preferably second heated surface temperatures and preferably dwelltime of melted material transferred through the passage.
 20. Anapparatus according to claim 1, further comprising a housing foraccommodating the first and second heated surfaces, the housing in fluidcommunication with a filter arrangement for filtering gases receivedfrom the housing, the apparatus further comprising a condenserarrangement positioned intermediate the housing and filter arrangement.21. A method of thermally compacting polymeric materials comprising thesteps of introducing polymeric material into a heating zone definedbetween first and second heated surfaces inclined downwardly towardseach other and being provided at their lower ends with a passage throughwhich polymeric material may drain.